1. Field of the Invention
This invention relates to improvements in a copper alloy, and more particularly to a copper alloy high in oxidation resistance and abrasion resistance at high temperatures and suitable for the material of frictionally sliding members of an engine such as a valve seat (or valve insert) and a valve guide for supporting a valve stem.
2. Description of the Prior Art
In recent years, automotive engines have been increasing in performance and power output, and therefore there has been a tendency that valve seats and valve guides are subjected to higher temperature and higher sliding bearing stress than conventional ones. Additionally, the valve seats and the valve guides have been required to have a better heat transmission in order to obtain both high power output and good fuel economy. Thus, high abrasion resistance and high coefficient of thermal conductivity have been required for the materials of the automotive engine parts such as the valve seats and the valve guides.
Research and development of such materials have been hitherto made around copper alloys. In this connection, the materials AlBC 1 to 4 (particularly AlBC 3) and similar AISI C95500 have been into practical use for valve seats or the likes. These materials are prepared by adding Ni and Fe to aluminum bronze. AlBC 1 to 4 are according to JIS (Japanese Industrial Standard) and discussed in a technical book "Non-Ferrous Metal", page 73, 14th edition, published in 1978 and written by Masataka Sugiyama and published by Korona-sha. AISI C95500 is discussed in "Metals Handbook 9th Edition Vol. 2", page 433, published in 1979 by American Society for Metals.
However, these conventional copper alloy are not sufficient particularly in abrasion resistance at high temperatures in case that they are used as the valve seat and the valve guide of an automotive engine which are subjected to severe conditions required to obtain the high performance and high power output of the engine. In other words, there is the possibility that the engine parts of the conventional copper alloys become large in abrasion amount under such severe conditions, and therefore the copper alloy are not suitable for the engine parts.